The present invention relates to a packaging method and packaging apparatus. More particularly, the present invention relates to a packaging method and packaging apparatus wherein a tray, having a flange and an opening surrounded by said flange on its upper face and containing an article to be packaged, is covered with a film over the opening and the film is welded to the flange.
Conventionally fresh fish and meat, as well as side dishes and other processed foods, have been packaged using the xe2x80x9coverlap method.xe2x80x9d The overlap method involves putting the food product into a tray and wrapping the entire tray with a film.
Consequently, the planar size of the film must be several times larger than the planar size of the tray because both the tray and the entire food product must be covered and the ends of the film must overlap in order to form a seal. Furthermore, such packages are often sealed by pressing a hot plate against the overlapped ends of the film on the bottom of the tray, which results in an inferior seal.
Meanwhile, there are some cases where another method (hereinafter called the xe2x80x9ctop-seal methodxe2x80x9d) is used instead of the overlap method. With the top-seal method, the film is placed only over the opening provided in the upper face of the tray and the film is thermally welded to the tray along the periphery of the hole. Using the top-seal method can reduce film consumption by half in comparison with the overlap method.
The top-seal method has been used chiefly for packaging shimeji and other varieties of mushroom. One common form of the top-seal method is to apply an adhesive to the sides of the tray around the opening and bond the ends of the film to the tray when the film is placed over the opening. Another common form is to sandwich the tray and a piece of film that is larger than the planar size of the tray between two tools and apply pressure and heat to thermally weld the film to the tray.
The disadvantage with both of these top-seal methods is that they require tooling matched to the size and shape of the tray. Consequently, industries that need to use multiple tray types to package a variety of different articles often use the overlap method instead of the top-seal method. Although the top-seal method provides such merits as reduced film consumption and improved sealing characteristics, it is often impractical because a separate set of tools must be prepared for each different size and shape of tray.
The object of the present invention is to provide a packaging method and corresponding packaging apparatus that allow an article placed on a tray to be sealed with a film using the top-seal method but do not require the preparation of tooling for each different size and shape of tray.
A packaging method in accordance with the first aspect of the invention is provided with first, second, third, and fourth steps. In the first step, the article to be packaged is put on a tray having an opening in its upper face; in the second step, the opening in the tray is covered with a film; in the third step, a heated hot member is touched, in a direction intersecting with a vertical direction, against the film on a portion of the tray near the opening where the film touches; and in the fourth step, at least one of the hot member or the tray is moved.
More specifically, in the first step of the packaging method described in the first aspect, a food product or other article is placed on a tray. In the second step, the opening in the upper face of the tray is covered with a film so that the film is touching a portion of the periphery of the tray opening. In the third step, the film on a portion of the tray near the opening where the film touches is pressed with a heated hot member in a direction intersecting with a vertical direction. In other words, the hot member is applied at an angle to a portion of the tray near the opening. In the fourth step, at least one of the hot member or the tray is moved while the hot member being applied at an angle to a portion of the tray near the opening. As a result, the entire portion of the film that is touching the tray in the area surrounding the opening is thermally welded to the tray.
With this method, since at least one of the hot member or the tray is moved, the hot member and the periphery of the tray opening are moved relative to each other. Consequently, various shapes and sizes of tray can be accommodated so long as the size of the tray is within certain limits. Unlike conventional top-seal methods, it is not necessary to prepare tools for each different type of tray or to spend time changing those tools each time a different tray is used. Therefore, equipment costs can be reduced and the efficiency of packaging operations can be improved.
Also, since the hot member is applied to a portion of the tray near the opening from a direction that intersects with a vertical direction, the hot member only comes in contact with a portion of the tray near the opening and does not come in contact with the portion of the film covering the tray opening. Consequently, the portion of the film that covers the opening is less likely to melt or develop tiny holes.
It is preferred that a pressure applying mechanism and controller be provided so that the pressure at which the hot member is applied to a portion of the tray near the opening and the speed at which the hot member and the periphery of the tray opening are moved relative to each other can be set to levels that are well matched to the materials from which the tray and film are made. It is also preferred that a controller and an angle adjustment mechanism be provided so that the degree to which the heating means heats the hot member and the angle at which the hot member is touched against the portion of the tray near the opening can be adjusted as necessary and appropriate.
A packaging method in accordance with the second aspect of the invention is a method as recited in the first aspect, wherein, either one or two or more hot members are touched against the film on a portion of the tray near the opening in the third step and either one or two or more hot members move along the periphery of the opening in the tray in the fourth step.
By touching two or more hot members against a portion of the tray near the opening, the amount by which each hot member must be moved along the periphery of the tray opening can be reduced in comparison with amount of movement required when only one hot member is used. That is, when only one hot member is used, the hot member must be moved at least one full revolution around the tray opening in order to weld the film to the entire periphery of the tray opening. But, when two or more hot members are used, the film can be welded to the entire periphery of the tray opening without moving each hot member a full revolution around the tray opening. Thus, the time required to move in the fourth step can be reduced and the efficiency of the packaging process can be improved.
Conversely, costs can be reduced when only one hot member is applied to a portion of the tray near the opening because, although the hot member must be moved at least one full revolution around the tray opening in order to weld the film to the entire periphery of the tray opening, fewer hot members need to be prepared.
A packaging method in accordance with the third aspect of the invention is a method as recited in the first or second aspect, wherein, during the third and fourth steps, the hot member not only thermally welds the film to a portion of the tray near the opening but also cuts the outer portion of the thermally welded film.
This method improves the efficiency of the packaging process because the film is welded and cut simultaneously.
It is also feasible to thermally cut the outer portion of the thermally welded film by using the hot member that welds the film to the tray. The hot member can thermally cut the film more reliably if a tensile force is applied to the film.
A packaging method in accordance with the fourth aspect of the invention is a method as recited in any one of the first through third aspects, wherein, during the fourth step, the hot member rolls as it moves along the periphery of the opening in the tray.
With this method, the frictional resistance between the hot member and the film on the tray is reduced because the hot member rolls on the tray (i.e., the hot member rotates as it moves along the tray). As a result, the film is less likely to melt or develop tiny holes.
Also, it is preferable for the face of the hot member that contacts the film to be made of a resilient material (such as resin or synthetic rubber) so that firm contact can be maintained between the film and the tray even when small irregularities exist on the surface of the tray.
A packaging method in accordance with the fifth aspect of the invention is a method as recited in any one of the first through fourth aspects, wherein, during the fourth step, the hot member is moved along the periphery of the opening in the tray by swiveling the hot member about a swivel shaft while planarly moving the swivel shaft.
A packaging method in accordance with the sixth aspect of the invention is a method as recited in any one of the first through fifth aspects of the invention. In the third step, a plurality of the hot members is touched against the periphery of the opening in the tray from above the stretch film. In the fourth step, the hot members are moved along the periphery of the opening in the tray by swiveling the plurality of hot members about the axes of at least two swivel shafts disposed in different planar positions.
A packaging apparatus in accordance with the seventh aspect of the invention is an apparatus, wherein a tray, provided with a flange and an opening surrounded by said flange on its upper face and containing an article to be packaged, is covered with a film over the opening and the film is welded to the flange. The packaging apparatus is provided with a hot member and a moving means. The hot member is capable of touching against the film on a portion of the flange of the tray, and the face of the hot member is capable of touching the tray is at an angle with respect to a horizontal plane. The moving means moves at least one of the hot member or the tray.
With the packaging apparatus described in the seventh aspect of the invention, the film is thermally welded to the flange by touching the hot member against the film on a portion of the flange of the tray. Then, when the hot member and the tray are moved relative to each other by the moving means, the hot member touches all portions of the flange and the film is thermally welded to the entire flange.
With this apparatus, since the hot member touches a portion of the flange and at least one of the hot members or the tray is moved, various shapes and sizes of tray can be accommodated so long as the size of the tray is within certain limits. Unlike conventional top-seal methods, it is not necessary to prepare tools for each different type of tray or to spend time changing those tools each time a different tray is used. Therefore, equipment costs can be reduced and the efficiency of packaging operations can be improved.
Also, since the face of the hot member is capable of touching the tray is at an angle with respect to a horizontal plane, the hot member only comes in contact with the flange of the tray and does not come in contact with the portion of the film covering a opening surrounded by the flange. Consequently, the portion of the film that covers the opening is less likely to melt or develop tiny holes.
A packaging apparatus in accordance with the eighth aspect of the invention is an apparatus as recited in the seventh aspect, wherein, the moving means moves the hot member against the tray.
A packaging apparatus in accordance with the ninth aspect of the invention is an apparatus as recited in the eighth aspect, wherein the moving means is provided with a swivel mechanism and a moving swivel shaft mechanism. The swivel mechanism swivels the hot member about a swivel shaft. The moving swivel shaft mechanism planarly moves the swivel shaft of the swivel mechanism.
With this apparatus, the swivel mechanism and the moving swivel shaft mechanism move the hot member. The moving swivel shaft mechanism can remain still when packaging trays with circular planar shapes or it can be operated when packaging trays with a large length-to-width ratio (or large rectangular trays). When the moving swivel shaft mechanism is used to move the swivel shaft while the hot member is being swiveled, shapes (and sizes) of tray that the hot member cannot follow using swiveling alone can be accommodated. That is, by combining movement of the swivel shaft with swiveling, the hot member can be moved along the entire flange of the tray.
Furthermore, when packaging trays having a large length-to-width ratio, the amount of time the hot member touches each part of the flange of the tray can be made more uniform by operating the moving swivel shaft mechanism. For odd-shaped trays as well, sealing can be accomplished by moving the swivel mechanism in both the X and Y directions.
Thus, since the apparatus described in this claim is provided with a moving swivel shaft mechanism, it can accommodate both odd-shaped trays and trays whose planar shape is rectangular or otherwise characterized by a large length-to-width ratio better than an apparatus that merely swivels the hot member around a fixed shaft.
A packaging apparatus in accordance with the tenth aspect of the invention is an apparatus as recited in the ninth aspect which is further provided with a controller. The controller controls at least one of the speed at which the hot member is swiveled by the swivel mechanism or the speed at which the swivel shaft is moved by the moving swivel shaft mechanism.
Since the packaging apparatus described in the ninth aspect is configured so that the hot member is moved along the flange by swiveling the hot member, the amount of time the hot member touches each part of the flange will vary if a constant swivel speed is used on any tray that is not circular in shape. This variance results in the occurrence of pinholes and defective sealing (i.e., failure to achieve a seal) in the seal area. In order to reduce this variance, this claim calls for controlling the speed at which the swivel mechanism swivels the hot member. Thus, the variance in the amount of time the hot member contacts each part of the tray can be reduced.
A packaging apparatus in accordance with the eleventh aspect of the invention is an apparatus as recited in the eight aspect, wherein a plurality of said hot members are provided. The swivel mechanism has at least two swivel shafts disposed in different planar positions. The swivel mechanism moves the plurality of hot members by swiveling at least one of the hot members about a first swivel shaft and swiveling at least one of the hot members about a second swivel shaft.
With this apparatus, the swivel mechanism is provided with multiple swivel shafts; a hot member swivels about a first swivel shaft while a hot member also swivels about a second swivel shaft. Since the positions of the first and second swivel shafts are planarly separated, the area over which the hot members can be moved is the total of the swivel areas of both swivel shafts. Therefore, even if the tray has a large length-to-width ratio, the hot members can be moved so that entire flange is accommodated by separating the two swivel shafts in the lengthwise direction of the rectangle. Furthermore, when packaging trays having a large length-to-width ratio, the amount of time hot members touch each part of the flange can be made more uniform.
Thus, since the swivel mechanism of the apparatus described in claim 11 is provided with multiple swivel shafts and swivels a hot member around each swivel shaft, it can accommodate trays whose planar shape is rectangular or otherwise characterized by a large length-to-width ratio better than an apparatus that merely swivels a hot member around a single fixed swivel shaft.
It is also feasible to control the apparatus so that it uses only one of the multiple swivel shafts and the hot member that swivels around that swivel shaft to conduct thermal welding on trays whose planar shape is circular (or otherwise has a length-to-width ratio close to 1).
A packaging apparatus in accordance with the twelfth aspect of the invention is an apparatus as recited in the eleventh aspect, which is further provided with a moving swivel shaft mechanism. The moving swivel shaft mechanism planarly moves at least one of swivel shafts.
With this apparatus, in addition to providing the swivel mechanism with multiple swivel shafts, the apparatus is configured so that the moving swivel shaft mechanism can move the swivel shafts planarly. Consequently, the apparatus can accommodate trays having even larger length-to-width ratios (or large rectangular trays). Furthermore, the amount of time the rollers touch each part of the flange can be made more uniform by precisely controlling the movement of the swivel shafts.
A packaging apparatus in accordance with the thirteenth aspect of the invention is an apparatus as recited in the twelfth aspect, which is further provided with a controller. The controller controls at least one of the speed at which the hot member is swiveled by the swivel mechanism or the speed at which the swivel shaft is moved by the moving swivel shaft mechanism.
A packaging apparatus in accordance with the fourteenth aspect of the invention is an apparatus as recited in the seventh aspect, wherein, the moving means moves the tray against the hot member.
A packaging apparatus in accordance with the fifteenth aspect of the invention is an apparatus as recited in any one of the seventh through fourteenth aspects, which is further provided with a film feeding means, a lift mechanism, and a hot member moving mechanism. The film feeding means feeds the film between the tray and the hot member. The lift mechanism lifts the tray and presses the flange of the tray against the film. The hot member moving mechanism moves the hot member and presses it against the film at a portion of the flange of the tray, which has been lifted by said lift mechanism.
With this apparatus, when a food product or other article is placed in a tray is lifted by the lift mechanism, the film has been fed between the tray and the hot member presses against the flange of the tray. When the hot member moving mechanism moves the hot member, the hot member is pressed against the film on a portion of the flange. Then, when the hot member and the tray are moved relative to each other by the moving means, the film is thermally welded to each portion of the flange.
A packaging apparatus in accordance with the sixteenth aspect of the invention is an apparatus as recited in any one of the seventh through fifteenth aspects, wherein a plurality of said hot members are provided. Hot members are so arranged that each hot member can touch a different portion of the flange of the tray.
Since multiple hot members are provided, the amount by which each hot member must be moved along the flange of the tray can be reduced in comparison with amount of movement required when only one hot member is provided. That is, when only one hot member is provided, the hot member must be moved at least one full revolution around the flange of the tray in order to weld the film to the entire flange of the tray. However, since this apparatus is provided with multiple hot members, the film can be welded to the entire flange of the tray without moving each hot member a full revolution around the flange.
Thus, the time required for the hot member moving means to move the hot members can be reduced and the efficiency of the packaging process can be improved.
A packaging apparatus in accordance with the seventeenth aspect of the invention is an apparatus as recited in any one of the seventh through sixteenth aspects, which is further provided with a controller. The controller controls the moving means to move at least one of the tray or the hot member so that the film is thermally cut at the outside of the thermally welded portion while being thermally welded to the tray.
With this apparatus, the hot member that thermally welds the film to the tray is used to thermally cut the outer portion of the thermally welded film. The film covers the tray and remains continuously connected to the film feeding means after the film is thermally cut. Therefore, the film feeding means can feed the film more smoothly and the film can be taken up more smoothly after cutting if a take-up means is provided which takes up the film that remains after the film is thermally cut.
Furthermore, the hot member can thermally cut the film more reliably if a tensile force is applied to the film.
A packaging apparatus in accordance with the eighteenth aspect of the invention is an apparatus as recited in any one of the seventh through seventeenth aspects, wherein, the hot member is a heat-emitting roller and rolls on the flange of the tray while the tray and the hot member are moving relative to each other.
With this apparatus, the hot member (heat-emitting roller) rolls on the flange of the tray. That is, the hot member rotates as it moves over the flange. Therefore, the frictional resistance between the hot member and-the film on the flange and the film is less likely to tear or develop tiny holes.
Also, it is preferable for the face of the hot member that contacts the film to be made of a resilient material (such as resin or synthetic rubber) so that firm contact can be maintained between the film and the flange even when small irregularities exist on the surface of the flange of the tray.
A packaging apparatus in accordance with the nineteenth aspect of the invention is an apparatus as recited in any one of the seventh through eighteenth aspects, wherein, the part of the hot member that touches the periphery of the opening in the tray is made of an elastomer containing silicon or fluoro rubber.
It is preferable for the face of the hot member that contacts the film to be made of a resilient elastic material so that firm contact can be maintained between the film and the tray even when small irregularities exist on the surface of the tray.
Therefore, with the apparatus described in claim 19, the part of the hot member that touches the flange of the tray is made of an elastomer containing silicon or fluoro rubber. The use of such an elastomer can also make it more difficult for the hot member to damage the surface of the tray as it rolls on the tray. Furthermore, an elastomer containing silicon or fluoro rubber is highly durable and therefore less susceptible to heat deterioration. Such elastomers also provide good heat conduction and improve efficiency, and they reduce damage to the film because of their superior surface release property.
Also, since the part of the hot member that touches the flange of the tray is made of an elastomer containing silicon or fluoro rubber, friction between a roller and the film to be necessary for rotation of the roller is improved if the hot member is the roller.